Tilapia Fry Research Articles

Growth Performance of Oreochromis Niloticus Fry Fed with Two Different Starter Diets

This study was conducted at Joseph Sarwuan Tarka University, Benue State, Nigeria to assess the growth performance of Nile tilapia (Oreochromis niloticus) fry fed Coppens and Skretting starter diets. A total of 200 fry were stocked at a density of 50 fry per 50 litre tanks. The experimental diets, Coppens and Skretting starter feeds were administered 4 times daily to satiation for a period 8 weeks (56 days) in two replicates per diet, utilizing four aerated plastic tanks. Weekly sampling was conducted to evaluate specific growth rate (SGR) and survival rate across the treatments. Statistical analysis revealed to significant differences (p>0.05) between the two diets treatment in terms of weight gain and length increment, although slight variations were observed. The average water temperature and pH during the experiment were 27.45°C ±0.77 and 7.35±0.15, respectively. The results indicates that both feed types performed comparably in promoting growth and survival rates of the fry. However, considering the higher costs of Coppens feed, Skretting starter feed is recommended as a more cost-effective alternative for aquaculture operations.

'Pasteurised' Tilapia: Drastic Mortality of Gyrodactylus cichlidarum During the Spring 2024 Heat Wave.

During spring 2024, a heat wave induced sustained water temperatures of 34°C during a week in Veracruz, Mexico. Serendipitously, we monitored Gyrodactylus cichlidarum infecting farmed tilapia fry during this pulse warming event and recorded a drastic decline of parasite populations over the following days. We subsequently established that parasites incubated invitro at ca. 27°C survived up to 24 h, while at ca. 30°C and 34°C, all worms died within 4-7 h. Abnormal haptor structures were observed in parasites that developed and were born at a water temperature of 34°C. Under farming conditions, no unusual fish mortality was recorded, suggesting that pulse heat treatment may be an effective method to control G. cichlidarum, a recognised tilapia pathogen.

Effect of Microplastic Exposure to the Reproductive Energy and Fecundity of Female Wami Tilapia (Oreochromis urolepis, Norman 1922) Fish

ABSTRACTThere is mounting evidence indicating that microplastics (MPs, < 5 mm) cause reproductive dysfunction in fish, yet information on the long‐term effects of MP exposure remains scarce. In this study, Wami tilapia fries were exposed to 38–45 µm polyethylene (PE) MPs for their first 2 months in treatment groups of control (0 PE MPs/mL), 1, 10, and 100 PE MPs/mL (with 60 individuals per group in triplicates), and subsequently maintained in a ratio of 3 females to 1 male for an additional 5 months. Reproductive proxies and parameters of female fish health were calculated, and models were developed according to the Akaike information criterion (AIC) and no significant differences in fecundity, relative fecundity, hepatosomatic index (HSI), weight, length, gonadosomatic index, and oocyte packing density were found between treatment groups (one‐Way ANOVA, p > 0.05). However, condition factors varied significantly between treatment groups (Kruskal–Wallis Test, p = 0.006), with the control group differing significantly from the groups exposed to 1 PE MPs/mL (p = 0.007), 10 PE MPs/mL (p = 0.03), and 100 PE MPs/mL (p = 0.001). Fecundity showed strong correlations with weight and length in all treatment groups except the group exposed to 10 PE MPs/mL (weight: r = 0.471, p = 0.346; length: r = 0.688, p = 0.131) and showed insignificant correlations with condition factors and HSI. Multiple regression models revealed that weight significantly contributed to fecundity in all treatment groups except the group exposed to 10 PE MPs/mL. Histopathological analysis indicated damage to livers and small intestines proportional to the dose of PE MPs. This study demonstrates that long‐term exposure of fish to MPs has no significant effect on fecundity but impairs fish health, which could potentially jeopardize the quality of fish eggs and recruitment.

Impact of Feeding Artemia franciscana Enriched with Various Oil Resources on Growth, Blood Biochemical and Behavioral Indices, and Survival of Oreochromis Niloticus

Abstract The main objective of the present trial was to examine the efficacy of feeding tilapia fry fish on Artemia franciscana diets supplemented with various oil emulsion resources in terms of performance, behavior indices, survival rate, blood biochemical parameters, and immunological response. Four hundred Nile tilapia fry (weighing 0.15±0.05 g and measuring 2.17±0.08 cm) were randomly allocated into four equal groups (each with five repetitions) and acclimatized for fifteen days. The first group served as the control and received unenriched Artemia franciscana (G0), while the remaining three groups were fed Artemia franciscana diets enriched with different oil resources (0.5 mL oil per liter for 6 hours): soybean oil (G1), sesame oil (G2), and rice bran oil (G3). Behavioral observations were recorded during the 45-day experimental period. At the end of the feeding trial, the chemical composition and fatty acid content of both Artemia and fingerlings were analyzed. Furthermore, the growth performance, survival, and immune response of the fingerlings were evaluated. The results indicated noticeable improvements in behavioral measurements (feeding, foraging and schooling), performance (final length, final weight, net weight gain, feed conversion ratio and specific growth rate), survival, and immune response among fry fish supplemented with enriched Artemia, particularly those enriched with soybean oil. Additionally, the chemical composition and fatty acid content of both Artemia and fish fry were significantly enhanced when oil emulsions are applied, with soybean oil demonstrating the most prominent improvements. Whereas, supplementing fry fish Artemia diets with oil resulted in lower liver enzyme activity and higher protein component levels in plasma in comparison to the control group. In brief, feeding Nile tilapia fry fish Artemia diets enriched with a soybean oil emulsion (0.5 mL/L) is recommended for promoting high performance, immunological activity, and survival throughout the early stage till fingerlings phase.

Impact of Arthrospira maxima Feed Supplementation on Gut Microbiota and Growth Performance of Tilapia Fry (Oreochromis niloticus)

Microalgae are promising as prebiotics in aquaculture. Arthrospira maxima has potential nutritional value but is poorly studied. We assessed A. maxima feed supplementation in tilapia fry and evaluated its effect on growth performance and gut microbiota. Fish were cultivated in ponds under 0%, 5%, 10%, and 15% A. maxima inclusion treatments. Growth parameters and biomass proximate analysis were assessed. A meta-amplicon analysis was performed on the gut microbiota using DADA2 and PICRUST2 for functional prediction. Among treatments, the 5% supplementation group seemed to present no negative effect on growth parameters and did not compromise the nutritional quality of tilapia fry biomass. Microbial composition was characterized by Cetobacterium, Pseudomonas and Aeromonas genera, and a predominance of beneficial metabolic pathways. Microbiota of tilapia fry fed with A. maxima showed unique genera with reported beneficial functions in tilapia. The abundance of potential pathogenic taxa was significantly decreased in supplementation treatments, possibly related to valuable compounds of A. maxima. The inclusion of the microalgae supported the stability of the microbiota, favoring the growth of commensal species. This seems to have an effect on decreasing the presence of pathogenic genera in the gastrointestinal tract. Overall, our work proposes 5% feed inclusion of A. maxima to be the most suitable for tilapia fry aquaculture to maintain production rates while improving general health.

Dmrt1 Is Responsible for Androgen-Induced Masculinization in Nile Tilapia.

17α-Methyltestosterone (MT) is a widely used androgen for all-male fish production in aquaculture. However, the molecular mechanism underlying MT-induced masculinization remains unclear. In this study, we aim to identify the key gene responsible for MT-induced masculinization using the Nile tilapia (Oreochromis niloticus) amhy, dmrt1, and gsdf mutants, which exhibit male-to-female sex reversal. Nile tilapia fry from these three mutant lines were treated with 50 μg/g MT from 5 to 30 days after hatching (dah). The results showed that amhy and gsdf mutants, but not dmrt1 mutants, were masculinized by the MT treatment. Gonadal transcriptome analysis revealed that genes involved in steroidogenesis and germ cell development in MT-treated dmrt1 mutants exhibited a similar expression pattern to that of the wild type (WT) XX. In addition, the dmrt1 mutants cannot be masculinized by co-treatment with MT and the aromatase inhibitor fadrozole. The MT treatment completely blocked early steroidogenic enzyme (Star2, Cyp17a2, and Cyp19a1a) expression independent of amhy, gsdf, and dmrt1. A luciferase analysis showed that MT directly suppressed basal and Sf-1-activated cyp19a1a promoter activity through ara and arb in cultured HEK293 cells. Furthermore, MT treatment inhibited germ cell proliferation in amhy and gsdf mutants but not in dmrt1 mutants. Consistently, dmrt1 expression was induced in MT-treated WT XX, -amhy, and -gsdf mutants. Taken together, these results suggest that dmrt1 is indispensable for MT-induced masculinization in Nile tilapia and that MT functions by inhibiting early steroid synthesis and activating dmrt1 to promote testis development.

Supplementing Nile tilapia (Oreochromis niloticus) (Linnaeus, 1758) larvae with dietary beta-glucan could improve their growth, survival, immune function, intestinal and liver histomorphology

Abstract Β-glucan exerts a positive impact and consider as a functional feed additives to enhance fish growth, immunity, control disease outbreaks and pathogen infections by increasing functional, immune and decreasing harmful responses. The present study aimed to determine the most effective dietary level of beta-glucan (βG) to improve Nile tilapia Oreochromis niloticus (L.) fry growth performance, feed utilization, and hematological indicators. Seven isonitrogenous (32% crude protein) and isocaloric diets (18 MJ/kg) were formulated. All diets were identical except for the variation in βG levels.The basal experimental diet (control diet) had no βG added. Diets 2–7 each contained βG at levels of 250, 500, 1000, 2000, 4000, and 8000 mg/kg diet, respectively. A total of 840 fish with an average body weight of 0.2±0.01 g were allocated into the seven experimental treatments (in triplicate). The trial lasted for 120 days, Nile tilapia fry growth performance and feed utilization were significantly (P≤0.05) higher in all treatments receiving βG diets than in the control diet. The fish fed with ßG0.1 diet showed the highest significant growth induces and the best FCR values. The survival (S%) of the fish also showed a significant increase in the βG diets up to ßG0.8 levels, when compared to the other experimental diet groups. All hematological parameters increased (P≤0.05) in fish fed with a diet supplemented up to ßG0.8 compared to the control group. Histological examination of the intestine and liver in the control group revealed histopathological alterations in the villi. On the other hand, the groups treated with βG had longer and structurally normal villi. The most well-preserved intestinal tissue and the tallest villi were observed in ßG0.1, followed by ßG0.050 and ßG0.8 groups. In the liver, the control group exhibited fatty degeneration, necrosis and pyknosis whereas the ßG0.1 group displayed the most preserved hepatic tissue, followed by ßG0.8 and ßG0.2 groups. The results indicate that according to FBW-based broken-line model analysis, the optimal dietary level of βG for Nile tilapia fry to exhibit superior growth and diet utilization efficiency associated with the best FCR for Nile tilapia should be 0.12% βG /kg diet. To increase the immunity of fish and improve the properties of hematological and histopathological indices, the dose can be increased to 0.8% βG without any adverse effects.

Optimization of Commercial Feed with Moringa Leaf Powder (Moringa oleifera) for the Growth of Nilem Fish Fingerlings (Osteochilus hasselti)

This study aims to test the impact of these additions on the growth of nilem fish Fingerlings. The research design was a completely randomized design (CRD) with six treatments and three replicates by adding moringa leaf meal (0%, 2%, 4%, 6%, 8%, and 10%) to commercial feed. The characteristics observed in this study included feed conversion ratio (FCR), specific growth rate, survival rate (SR), absolute length and weight growth, and water quality. Analysis of variance (ANOVA) was used to evaluate the data, and Duncan's test was performed subsequently. The results showed that although there was no significant effect (P>0.05) on tilapia fry or survival rate (SR), the addition of moringa leaf meal to commercial feed had a significant effect (P<0.05) on tilapia larval growth in terms of absolute length and weight growth, specific growth rate, and Feed Conversion Ratio (FCR). The ideal composition for nilem Fingerlings development was 6%; the absolute values for length and weight growth were 1.13 cm and 0.33 g, the specific growth rate was 1.27%/day, the FCR was 1.41, and the survival rate of nilem fry was 93.33%.

Exploring the presence of tilapia species in a central western Mexican reservoir using mitochondrial DNA control region sequencing

Oreochromis niloticus is the most important aquacultural species worldwide. Several countries are interested in repopulating natural or artificial reservoirs with the fry of tilapia (Oreochromis sp.) to develop new fisheries or to enhance the existing ones. However, as tilapia is considered an invasive species, it is essential to check the existence of the species in the place before releasing any fry. Characterization of tilapia species with meristic is unreliable because of existing morphological similarities among species. In this work, the composition of the tilapia species of Laguna El Mastranzo (LEM), Nayarit, Mexico, was explored for the first time through a molecular method using the mitochondrial DNA control region. Three tilapia species (Oreochromis niloticus, O. aureus, and O. urolepis) were found in LEM, and it was confirmed that the two commercial strains (Aquamol and Spring) intended for repopulation were O. niloticus. Seven haplotypes of mitochondrial DNA control region sequences were obtained: three in LEM, three in Aquamol, and one in Spring strains. Before repopulating any reservoir, a molecular verification strategy is recommended to avoid spreading the species. The results of this work represent a glimpse into the genetic material of LEM, Nayarit, Mexico.

The effect of the ratio of male to female Broodstock on the production of tilapia (Oreochromis niloticus) Seed

This research was conducted from November to December 2023 at the Production Centre of Pangkajene Fish Seed Institute, Sidenreng Rappang Regency, South Sulawesi Province. The objective of this study was to determine the effect of the ratio of male and female broodstock on tilapia seed production, and to determine the ratio of male and female broodstock that produce the most seed production. The design used was a completely randomised design with 4 treatments and 3 replications. The data obtained were presented in the form of graphs and tables. The effect of treatment was analysed using analysis of variance (ANOVA) followed by Tukey's test. The results of the analysis showed that the ratio of male to female broodstock had a significant effect on tilapia fry production (P < 0.05) Sig = 0.034. The highest seed production was found in treatment C (1 male: 4 females) with an average production of 71,000 seeds. Treatment B (1 male: 3 females), 51,000 seeds, treatment D (1 male: 5 females), 34,000 seeds and treatment A (1 male: 1 female) with an average production of 21,000 seeds. It can be concluded that the ratio of male to female broodstock has a significant effect on the production of nila fish fry (Oreochromis niloticus). The highest fry production was obtained in the ratio 1 male; 4 females.Keywords: Broodstock; Production; Ratio; Seed; Tilapia

Addition of Probiotics to Feed on the Growth and Survival of Tilapia Fish Seeds

Introduction: Tilapia (Oreochromis niloticus) is one of the leading commodities of freshwater aquaculture in Indonesia. The problem that is often experienced by farmers is the absorption of fish feed nutrients that are less than optimal, due to the low quality of feed raw materials. The study aims to determine the effect of adding probiotics to feed on growth and survival, in tilapia (O. Niloticus) fry. Method: The test organisms used in this study were tilapia (O. niloticus) as many as 200 fish with an initial weight of 1.09-1.28 g/head. Tilapia seeds were obtained from UPR Saluyu, Dolo sub-district, Sigi district, Central Sulawesi. The design used was a complete randomized design (CRD). Results and Discussion: Variables observed were daily weight growth rate (LPBH), absolute weight growth (PBM), survival rate, feed conversion ratio (CTR), and water quality. Conclusion: The results showed that the highest absolute weight growth in tilapia was found in treatment D (8 mL probiotics) which was 2.04 g, the specific growth rate was (2.86% / day), and the feed conversion ratio produced (1.57), while the survival rate of tilapia obtained during maintenance was (80.00-84.00%).

High stocking density affected the growth performance, digestive enzyme activity, intestinal histology, and immune response of Nile tilapia (Oreochromis niloticus) fry grown in brackish water

Abstract It is crucial to ensure the suitable stocking density for Nile tilapia fry since Nile tilapia is among the most consumed fish species globally. In this study, fry were distributed at three stocking densities, 1000 fry/m3 (low density, LD), 2000 fry/m3 (middle density, MD), and 4000 fry/m3 (high density, HD). Then each stocking density was subdivided into two groups where three aquaria were supplied with fresh dechlorinated water (FW, 0.35 g saline /L), and the other three aquaria were fortified with underground brackish water (BW, ≈ 8 g saline /L). Subsequently, fry were kept under these experimental conditions and offered 40% crude protein thrice daily at 4–5% of the body mass for 15 days, then switched to 30% thrice daily at 3–4% of the body mass until the end of the trial (60 days). Except for the dissolved oxygen, salinity, and total ammonia nitrogen, the measured water characteristics (temperature and pH) were not markedly (P˃0.05) affected by the stocking density or water salinity. Stocking density was a significant factor in the case of final body weight, weight gain, specific growth rate, and survival rate (P<0.05). The water salinity and stocking density markedly affected the digestive enzyme activity (protease, lipase, and amylase) (P<0.05). The stocking density, water salinity, and their interaction were significant factors in the lysozyme activity. The stocking density significantly affected the superoxide dismutase (SOD), catalase activity (CAT), and glutathione peroxidase (GPx), and fish fry in LD showed higher SOD, CAT, and GPx than fish in MD or HD in FW or BW (P<0.05). Malondialdehyde (MDA) was affected by the stocking density, and fish fry in LD showed lower MDA than in MD or HD under FW or BW (P<0.05). Increased density to HD in the FW or BW induced slight degeneration of the intestinal mucosal lining. In conclusion, Nile tilapia fry can grow in brackish water (≈ 8 g saline /L) with 1000 to 2000 fry/m3 without affecting growth performance, feed utilization, digestive enzymes, intestinal histological features, and immune and antioxidative responses.

Comparable to 17α- methyl testosterone, dietary supplements of Tribulus terrestris and Mucuna pruriens promote the development of mono-sex, all-male tilapia fry, growth, survival rate and sex-related genes (Amh, Sox9, Foxl2, Dmrt1)

To evaluate Tribulus terrestris and Mucuna pruriens for inducing all-male tilapia, mixed-sex Nile tilapia, Oreochromis niloticus, (mean weight 0.025 ± 0.009 g; mean length 1.25 ± 0.012 cm), were given a meal supplemented with either T. terrestris powder (commercial fish feed, 40% crude protein) (TT group), M. pruriens seed extract (MP group), MP + TT (mixed group), 17α-methyl testosterone (MT, control positive), or without supplements (control negative). The MP extracts significantly increased (P < 0.05) the final weight, weight gain, weight gain rate, and specific growth rate while feed conversion ratio was significantly decreased (P < 0.05). Plant extracts markedly improved (P < 0.05) the survival rate, proportion of males, and total testosterone compared to control and MT. Estrogen levels were lower in groups with plant extract than other groups. Fifteen days post-feeding, the Amh gene was expressed in the brain of O. niloticus fries with higher levels in MP, TT, and MT groups. Additionally, the expression of the Sox9 and Dmrt1 genes as a male related genes in fish fry gonads revealed significantly (P < 0.05) higher levels in groups fed on MP, TT, and MT compared to control after 30-day post-feeding, whereas; Foxl2 gene expression as a female related gene was significantly (P < 0.05) lower in fish fed on MP, TT, and MT compared to other groups after 30 days post feeding. Histologically, MT, MP, TT, and the mixture all exhibited solely male reproductive traits without noticeable abnormalities. This study concluded that each of the TT or MP extracts can induce sex reversal in tilapia while having no negative health impact compared to MT as the growth and survival rate in the treated groups with TT and MP were higher than control and group treated with MT.

Effect of fermented rice bran as a carbon source for rearing genetically improved farmed Tilapia, Oreochromis niloticus (Linnaeus, 1758), fry in biofloc system

Fermented rice bran, when used as a carbon source in a biofloc system, can improve water quality, growth, and feeding efficiencies of cultured species. The present study delves into the effect of fermented rice bran as a carbon source on the growth and survival of Genetically Improved Farmed Tilapia (GIFT) fry. Additionally, the study investigated its impact on water quality, intestinal histology, proximate composition of fish and biofloc, total plate count of the experimental tank, and fish gut in the biofloc system. The study employed a completely randomized design with five different treatments: NFRB+BFT (Non-Fermented Rice Bran), FRBW+BFT (Fermented Rice Bran with Water), FRBP+BFT (Fermented Rice Bran with Probiotic), FRBY+BFT (Fermented Rice Bran with Yeast), and a clear-water system (with daily water exchange of 10%). The experimental duration was 60 days. The GIFT fry with an average weight of 1.04 ± 0.02 g were randomly distributed in High Density Polythene (HDPE) tanks of 110 L capacity at a stocking density of 250 individuals (ind.) m−3. Results indicated that the weight gain %, length gain %, Specific Growth Rate (SGR), and Protein Efficiency Ratio (PER) in FRBP+BFT and FRBY+BFT treatments were similar, with no significant differences (p > 0.05) and significantly higher (p < 0.05) than other treatments. At the end of the experiment, FRBP+BFT and FRBY+BFT treatments showed lower ammonia-N values. The histological study of GIFT showed a number of villi and villi length in FRBP+BFT and FRBY+BFT were similar with no significant differences (p > 0.05). The protein, lipid, and ash content of fish and biofloc were similar with no significant differences (p > 0.05) in FRBP+BFT and FRBY+BFT treatments. The total plate count of fish gut and water in FRBP+BFT and FRBY+BFT treatments was similar and significantly higher (p < 0.05) than the other treatments. Overall, the results indicate that rice bran fermented with both probiotic and yeast as a carbon source showed similar growth performance and improved water quality in rearing GIFT fry in a biofloc system.

Influence of interaction between feeding schedule and long-term starvation on biological indicators, intestine histological and body biochemical of Nile tilapia(Oreochromis niloticus) fry

Influence of interaction between feeding schedule and long-term starvation on biological indicators, intestine histological and body biochemical of Nile tilapia(Oreochromis niloticus) fry

Fishmeal substitution by zooplankton or Daphnia magna biomass meals in the diet of Nile tilapia: Effectson growth, gut histological changes, bacterial abundanceand stress tolerance.

Fishmeal substitution with sustainable feed sources is highly essential towards sustainable production. This study aimed to investigate the effects of substituting fishmeal (FM) with Daphnia magna biomass meal (DBM) or zooplankton biomass meal (ZBM) on growth performance, liverand intestinal histology, gut bacterial abundanceand stress tolerance of Nile tilapia, Oreochromis niloticus, fry. Nile tilapia fry (0.23 ± 0.04 g) were randomly assigned to five groups of three replicates. The control diet comprised 300 g/kg FM, and the FM was substituted with DBM or ZBM at levels of 25% and 50% (DBM-25, DBM-50, ZBM-25and ZBM-50respectively) in the other experimental diets. The experiment lasted 56 days in 1.5 m3 concrete tanks. The results revealed that weight gain andfeed conversion ratio(FCR) significantly (p ≤ 0.035 and 0.025respectively) improved with a polynomial response with a peak at 25% ZBM and a linear increase with DBM up to 50% of FM. Histometric indices of the distal intestine showed improvements (p ≤ 0.001) in villus height, villus width, crypt depthand muscle thickness of fish fed DBM or ZBM compared to the control. In the meantime, there were no histological abnormalities in the liver sections. The replacement of FM with DBM or ZBM could modulated gut bacterial abundance, including total bacterial count, Escherichia coli, Bacillus subtilis, and Lactobacillus sp. The fish-fed DBM or ZBM-containing diets had higher (p ≤ 0.05) tolerances to salinity stress than the control group. In conclusion, DBM or ZBM could replace FM up to 50% and 25%, respectivelywith improved fish growth performance, FCR, gut histologyand tolerance to salinity stress.

Integration of fruit in the formulation of feed for Oreochromis niloticus breeding in the region of Vakinankaratra, Madagascar

To promote the nutrition of tilapia in farming, four foods were created using traditional raw materials and containing different quantities of locally produced banana flour. These foods, which contain 36% crude proteins and 8% lipids, were tested on tilapia fry with an initial weight of 8 grams. After 50 days of the experiment, the final weights of the fish fluctuated between 33.28 grams and 41.4 grams, depending on the treatments used. Foods containing 3% and 6% banana flour showed the highest growth and food conversion rates, with respective specific growth (SGR) rates of 3.98 and 3.62, as well as conversion rates (CI) of 1.8 and 1.69. Meanwhile, the food with 10% banana flour obtained a SGR of 2.92 and a CI of 2.01, while the control obtained a SGR of 3.3 and CI of 1.7. Thanks to this test, we were able to observe the impact of bananas on the premature development of tilapia. We will continue to study the use of local agri-food byproducts and waste in feeding this fish.

Report on Mortalities of Nile Tilapia (Oreochromis niloticus) Due to Tilapinevirus tilapiae and Co-infecting Bacteria in Winter Season

Background: Tilapinevirus tilapiae, commonly known as Tilapia lake virus, is a major viral infection of cultured tilapia, causing severe rates of fatalites and has evolved as a serious hazard to the tilapia in the world. Predisposing factors, notably temperature and the development stage of the host play a decisive role in influencing the extent of pathogenesis and the mortality rate associated with the disease. The seasonality of TiLV outbreaks has been observed in multiple countries, with a higher frequency occurring during the summer months. Methods: In the current investigation, the occurrence of TiLV disease was examined in fry and fingerlings of tilapia during the winter season (January - February, 2020) in Pune District, Maharashtra, India. The disease was observed in fish reared in open cages (Case I) and in nursery rearing farm (Case II). Infected tilapia displayed generalized gross clinical signs. TiLV was identified and confirmed in both instances using a semi-nested reverse transcriptase PCR by amplifying TiLV genome segment 3 and further confirmed by histopathogical investigation. Result: The research demonstrated the vulnerability of early developmemtal stages of O. niloticus to TiLV disease, suggesting the potential occurrence of this infection during the winter season, characterized by lower temperatures. Additionally, microbial investigations exposed the prevalence of Aeromonas spp., predominantly associated with TiLV-positive fish. These results align with previous publications, underscoring the potential role of bacterial infectious agents (Notably aeromonads), in exacerbating TiLV disease during outbreaks.

Anesthetic Efficacy of Lavender and Lemongrass Essential Oils in Nile Tilapia (Oreochromis niloticus, i-Excel strain) Fry

Anesthetics play a crucial role in aquaculture by ensuring the welfare and health of fish, facilitating various procedures, and preventing physical injuries during handling. Recently, plant- based anesthetics for fish are becoming a sustainable alternative to synthetic anesthetics in aquaculture and fisheries research. The present study examined the use of lavender (Lavandula angustifolia) and lemongrass (Cymbopogon citratus) essential oils as anesthetics for Nile tilapia Oreochromis niloticus(i-Excel strain) fry. Fish (average body weight = 0.004 g) were immersed in varying concentrations of 40, 50, 60, 70, and 80 μL L-1 and 30, 40, 50, 60, and 70 μL L-1 for lavender and lemongrass essential oils, respectively. The induction and recovery times were recorded and the best dose was determined based on rapid induction (&lt;3-4 minutes) and quick recovery (&lt;10 minutes). The results indicated that both essential oils exhibit dose-dependent effects on sedation and recovery. Lavender essential oil achieved optimal anesthesia at 60 μL L-1 , with an induction time of 229.3±10.7 seconds and a recovery time of 310.9±16.9 seconds, while lemongrass essential oil induced optimal anesthesia at 30 μL L-1 , with an induction time of 232.5±11.7 seconds and a recovery time of 130.5±8.6 seconds. Both concentrations for both essential oils resulted in 100.0% survival, while higher doses induced faster anesthesia and recovery but decreased survival rates. These essential oils offer cost-effective alternatives to synthetic anesthetics for short-term handling procedures; however, further research on histopathological effects and optimal transport dosages is needed.

Effect of the combination of fluoxymesterone and a commercial blend of additives on the sex proportion, growth, and survival of Nile tilapia (Oreochromis niloticus) fry

In the commercial culture of Nile tilapia (Oreochromis niloticus), monosex, all-male populations obtained through steroid sex reversal is the most commercially used method to eliminate unwanted reproduction and increase final productive and economic yield. However, the rapid growth of Nile tilapia culture has led, in some regions, to an increase in infectious diseases and mortality in all stages of commercial culture. To reduce this, without the abuse of antibiotics or similar substances, feed additives are currently used in all stages, including the fry period, during the sex reversal process. The objective of this work was to evaluate the effect of synthetic steroid Fluoxymesterone (FM) at various concentrations in combination with a commercial Blend of additives (BA) on the percentage of males, growth, and survival of Nile tilapia fry. Five treatments (FM20, FM5+BA, FM10+BA, FM20+BA, and BA+FM20) and a control group were evaluated. Treatments differ in the order in which the commercial blend (2 g) was added and the FM concentration (5, 10, and 20 mg). The feeding trial lasted for 30 days using a sexually undifferentiated population of Nile tilapia. The results showed a decrease in the percentage of males in all treatments supplemented with the BA, compared to the FM20 treatment (containing 20 mg without BA). Growth and survival were positively affected by the inclusion of the BA in all treatments, showing higher values than those observed in the control group. Further studies are necessary to determine the FM-BA interaction.